1. Field of the Invention
The present invention relates to a wireless system utilizing microwave frequencies to provide bi-directional transfer of programming information between a common focal point and a plurality of remote locations. More specifically, the present invention relates to the use of Multichannel Multipoint Distribution System (MMDS) frequencies to receive programming at remote locations and Multipoint Distribution System (MDS) frequencies to transmit information/data from remote locations.
2. Statement of the Problem
Consumers receive television programs one of four ways. Historically, television programming was broadcast from a central antenna to a number of rooftop antennas within a given radius of a transmitting tower. Cable then became available and allowed a much higher quality delivery of television programming to a consumer's household. While the quality of the programming substantially increased, the consumers encountered a significant increase in costs for such programming. Satellite dish antennas (TVRO) represent a third delivery system. An individual consumer pays several thousand dollars for the TVRO delivery system and also pays a monthly charge for the programming. TVRO systems allowed consumers in rural areas, however, to receive high quality programming via satellite where conventional television signals and cable would not provide delivery. The fourth type of delivery system is commonly called "wireless cable."
In a sense, wireless cable represented a return to the historical conventional delivery of television signals. A consumer purchased a rooftop microwave antenna and pointed it to a common microwave transmission source usually mounted on the top of a tower or a high location such as a mountain top. The initial "wireless cable" systems operated on the MDS frequency range of 2150 MHz to 2162 MHz. Limited programming over one or two channels was provided under MDS frequencies. With the advent of Multichannel Multipoint Distribution Systems (MMDS), with a frequency range of 2500 MHz to 2686 MHz, a plurality of channels could be simultaneously provided to the rooftop microwave antenna. MMDS "wireless cable" systems are becoming popular nationwide and, in fact, worldwide, principally in comparison to the much greater expense of purchasing and installing cable. For example, in a community of five-acre home sites, the laying of cable would be prohibitively expensive whereas provision of wireless cable to such sites would be significantly less costly.
Developing simultaneously, with the development of television programming systems, as described above, is the need to provide feedback from the consumer to the program delivery source such as, for example, pay per view (PPV) systems. Cable systems have the unique advantage of providing a solid two-way connection path between the consumer and the source of programming. In TVRO and wireless cable systems, no such link exists and the consumer must rely on making a phone call to the programming source (or other location) to order pay per view programming. Pay per view programming is used as an example and it is to be understood that many other services contemplate a return data transmission path from the consumer to the source of programming (for example, ordering of merchandise, computer data, etc.).
General Instruments currently manufactures a set top that provides for a standard telephone hook up for sending data back to the billing computer. This system is identified as Model No. 1507 MU and is available from General Instruments, 2200 Byberry Road, Hatboro, Pa. 19040. This system is easily installed by a customer to access pay per view programming. Hooking up a telephone line to every set top, however, is costly and the customers are sometimes on a long distance exchange or party line.
A need exists for a wireless cable system to provide a return information/data path back to the source of programming. The system implementing this must provide the return data path using the available frequencies and at a low cost to the consumer. The service must use the existing equipment as much as possible.
Presently, Instructional Television Fixed Service (ITFS) response frequencies (2686.0625 MHz to 2689.8125 MHz) are being considered for use as return link frequencies by the FCC. See FCC General Docket No. 90-60. This approach is somewhat expensive and elaborate due to the fact that the receive and transmit frequencies are so close to one another--normally requiring separate receive and transmitting antennas and a separate down converter for receiving the ITFS signal and for the transmitter (low power for sending back the return audio link). The power required for the return link is relatively small (less than 100 milliwatts) but, due to the close proximity of the frequencies, overload of the receive down converter is a problem. Another problem exists with using ITFS response frequencies in that interference and disruption of the service may result. The close proximity of ITFS response frequencies (2686.0625/2689.8125 MHz) to ITFS/MMDS band (2500/2686 MHz) would require physically large, high Q and expensive filters to minimize interference between transmit and receive signals.
While it has been suggested to use the existing MDS frequencies to return information/data, no system presently exists.
A need, therefore, exists to enable wireless cable operators and users to utilize the MDS frequencies for pay per view programming, computer links, banking, home shopping, medical alarm, and fire/security as well as to receive standard programming at a minimum cost. Heretofore, this has only been available to wireless consumers through use of standard telephone hookups.
Solution to the Problem
The present invention provides a solution to the above stated problem by providing a two way or bi-directional transfer of programming and information/data between a common transmission point such as a tower and each of a plurality of remote locations such as consumers' house. The present invention accomplishes this by utilizing the same microwave antenna at a consumer's house for receipt of programming and for transmission of data. A unique bi-directional converter is utilized to down convert the microwave programming signals and to up convert data microwave transmission signals. The converter operates using overlapping or common components to minimize the cost to the consumer. The present invention utilizes a mast mounted receive/transmit converter that incorporates a common local oscillator to down convert incoming microwave television signals while simultaneously up converting outgoing information and data signals to the transmission tower. The present invention utilizes the existing MMDS frequencies to down convert programming signals to the remote locations and provides a new use for the existing MDS frequencies to transmit information/data from the remote locations to the common transmitter.